The use of tooling balls rigidly secured on a mechanism is known to locate reference positions on the mechanism. Examples of such mechanisms are manufacturing equipment, robotic apertures, and devices subject to expansion or contraction where close dimensional tolerances must be maintained. Coordinate measuring machines precisely determine the position of the center of each tooling ball used. Often, these coordinate measuring machines are optical systems using lasers; such as laser trackers. Typically, a hand-held reflective device is positioned against the sphere of the tooling ball to reflect a beam of light from the laser back to the coordinate measuring machine. The reflective device is then moved manually to other locations on the sphere to again reflect a beam of light back to the coordinate measuring machine. This procedure continues until enough positions on the sphere of the tooling ball have been determined to precisely locate of the center of the sphere. The entire procedure is repeated each time it is desired to check for movement of the mechanism. Thus, determining the center of the sphere of a tooling ball in this manner is time consuming. Additionally, since the reflective device is often moved around the tooling ball by hand, the procedure is cumbersome and tiring for the users.
Attempts have been made to simplify this procedure by replacing conventional tooling balls with devices whose center is more easily determined. However, in addition to requiring the discarding of conventional tooling balls, such devices are often expensive, less durable, and/or bulky.
Examples of prior tooling ball related devices and of prior optical measuring systems are disclosed in the following U.S. Pat. Nos.: 3,188,739 to Olsen et al.; 3,730,470 to Mitchell; 4,543,729 to Holbrook; 4,621,926 to Merry et al.; 4,714,339 to Lau et al.; 4,790,651 to Brown et al.; 4,964,218 to Morghen; 5,007,175 to Schwarz; 5,073,005 to Hubbs; 5,119,564 to Hamilton et al.; 5,177,563 to Everett et al.; 5,231,539 to McMillen; 5,305,091 to Gelbart et al.; and 5,530,549 to Brown, the disclosures of which are hereby incorporated herein by reference. Another prior device and optical measuring system is disclosed in WO 95/35480 to Ehbets.
Thus, there is continuing need to provide improved devices for determining the location of a point in space, especially for determining the center of the sphere of a tooling ball.